The present invention is drawn to the area of ink-jet imaging. More specifically, ink-jet prints can rapidly printed and stacked in a receiving tray without substantial smearing of the printed image or ink transfer to the back of adjacent media.
In recent years, computer printer technology has evolved to a point where very high resolution images can be transferred to various types of media, including paper. One particular type of printing involves the placement of small drops of a fluid ink onto a media surface in response to a digital signal. Typically, the fluid ink is placed or jetted onto the surface without physical contact between the printing device and the surface. Within this general technique, the specific method that the ink-jet ink is deposited onto the printing surface varies from system to system, and can include continuous ink deposit and drop-on-demand ink deposit.
With regard to continuous printing systems, inks used are typically based on solvents such as methyl ethyl ketone and ethanol. Essentially, continuous printing systems function as a stream of ink droplets are ejected and directed by a printer nozzle. The ink droplets are directed additionally with the assistance of an electrostatic charging device in close proximity to the nozzle. If the ink is not used on the desired printing surface, the ink is recycled for later use. With regard to drop-on-demand printing systems, the ink-jet inks are typically based upon water and glycols. Essentially, with these systems, ink droplets are propelled from a nozzle by heat or by a pressure wave such that all of the ink droplets ejected are used to form the printed image.
There are several reasons that ink-jet printing has become a popular way of recording images on various media surfaces, particularly paper. Some of these reasons include low printer noise, capability of high speed recording, and multi-color recording. Additionally, these advantages can be obtained at a relatively low price to consumers. However, though there has been great improvement in ink-jet printing, accompanying this improvement are increased demands by consumers in this area, e.g., higher speeds, higher resolution, full color image formation, increased stability, etc. As new ink-jet inks are developed, there have been several traditional characteristics to consider when evaluating the ink in conjunction with a printing surface or substrate. Such characteristics include edge acuity and optical density of substrate, lack of deviation of ink droplets, presence of all dots, resistance of the ink after drying to water and other solvents, long term storage stability, and long term reliability without corrosion or nozzle clogging. Though the above list of characteristics provides a worthy goal to achieve, there are difficulties associated with satisfying all of the above characteristics. Often, the inclusion of an ink component meant to satisfy one of the above characteristics can prevent another characteristic from being met. Thus, most commercial inks for use in ink-jet printers represent a compromise in an attempt to achieve at least an adequate response in meeting all of the above listed requirements.
In general, ink-jet inks are either dyexe2x80x94or pigment-based inks. Both are typically prepared in an ink vehicle that contains the dye and/or the pigment. Dye-based ink-jet inks generally use a liquid colorant that is usually water-based to turn the media a specific color. Conversely, pigmented inks typically use a solid or dispersed colorant to achieve color.
Papers used for ink-jet printing have typically included high-quality or wood-free papers designed to have a high ink absorptivity. These papers are functionally good for ink-jet printing because the ink-jet inks may be absorbed readily and dry quickly. However, such papers often do not allow for a crisp or sharp image. Thus, in order to attain enhanced print quality and image quality as in a photograph, special media has been developed to work with aqueous inks. For example, various coating coated papers (art paper, coat paper, cast-coat paper, etc.) have been prepared by coating a layer comprising a hydrophilic binder and an inorganic pigment or particulate on a paper substrate. Additionally, recording sheets have been prepared by coating an ink absorptive layer on paper or other supports, e.g., transparent or opaque plastic film supports. An example of such specialty media utilizes a swelling-type ink absorptive layer, e.g., gelatin, polyvinyl alcohol, methyl cellulose, and the like. Though swellable media provides a relatively good substrate with respect to certain image quality properties, a drawback includes the fact that swellable media requires more dry-time than other types of media. As digital imaging becomes more popular, and ink-jet output devices continue to push photo printing speeds, it has become increasingly important for ink-jet prints to be able to be stacked in a printer output trays without smearing the printed image or sticking to adjacent media sheets. In other words, as a by-product of rapid printing speeds, printed media must often be stacked before the printed image is sufficiently dry to prevent smearing or ink transfer. Though this problem is especially prevalent when using swellable media, it can be a problem with nearly all other types of media as well, depending on the ink, substrate, and print speed selected for use.
It has been recognized that ink-jet printing media can be prepared that minimizes ink transfer from the front of a printed media sheet to the back of a second media sheet when stacked in a printer output tray. It has been further recognized that such ink-jet printing media, upon printing and stacking, provides decreased gloss loss and/or surface damage of the printed image.
With this in mind, a coated substrate for ink-jet ink printing can comprise a printing surface and an opposing back surface, wherein the printing surface comprises a coating formulated for accepting an aqueous ink-jet ink composition, and the back surface comprises a coating formulated for repelling the aqueous ink-jet ink composition.
Additionally, ink-jet ink printing media can comprise a paper substrate having a first side and an opposing second side; a hydrophilic polymeric material coated on the first side and the second side of the substrate; and a substantially hydrophobic polymeric composite material coated over the hydrophilic polymeric material on the second side of the substrate.
Next, a composite coating material for overcoating hydrophilic coated printing media can comprise a polymeric blend of a hydrophilic polymeric binder and a hydrophobic polymeric binder, wherein the polymeric blend has a hydrophilic polymeric binder to hydrophobic polymeric binder ratio from 1:5 to 1:1 by weight; and hydrophobic beads dispersed within the polymeric blend, wherein the polymeric blend to hydrophobic bead ratio is from 1:9 to 8:2 by weight.
Next, a coated substrate for ink-jet ink printing can comprise a printing surface and an opposing back surface, wherein the printing surface comprises a coating formulated for accepting an ink-jet ink composition, and wherein the back surface comprises a backcoating formulated for repelling the ink-jet ink composition. In this embodiment, the backcoating can comprise a hydrophobic polymeric binder blended with a natural wax, for example.